'TDARES 9911F': a heat-tolerant leafy radish line

Leafy radish (Raphanus sativus L. var. oleiformis Pers.) is rich in β-carotene, ascorbic acid, α-tocopherol, and quercetin, and is gradually being considered as a new and alternative leafy vegetable. However, current leafy radish cultivars grown in Taiwan are heat intolerant, thus cannot be grown as summer vegetables. Therefore, developing new leafy radish cultivars with heat tolerance is of interest to breeders and is needed. 'TDARES 9911F' was selected using maternal line selection for four generations and evaluating its horticultural characteristics, yield, uniformity, and cell membrane thermostability (CMT) in summer from 2007 to 2010 followed by comparative and regional trails in 2011 and 2012. In summer, 'TDARES 9911F' required 21 days from sowing to harvest. The plants were approximately 30 cm tall and leaves were narrow and oblong, with a mild incision margin, and a wrinkled surface without trichomes on the abaxial and adaxial sides. The leaf texture was relatively soft and flexible and the flavor was mildly astringent and slightly sweet. The yield, plant height, fresh shoot weight, and root length of 'TDARES 9911F' was unaffected by high temperatures (40/35°C) as well as crude fiber, vitamin C, and total soluble sugars content. In addition, 'TDARES 9911F' was as susceptible to the disease black rot (Xanthomonas campestris pv. campestris) at both 25/20 and 40/30°C. Therefore, we concluded that line 'TDARES 9911F' has potential as a new summer leafy vegetable.